iOS Application Lifecycle

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Mobile apps for iPhone & iPad

Table of Contents iOS app Execution model

UIApplication object

UIApplicationDelegate object

UIViewController Lifecycle

Events

State

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UIApplicationExecution model and lifecycle

Execution model – Entry Point

iOS Application main function:

#import <UIKit/UIKit.h>#import "AppDelegate.h"

int main(int argc, char * argv[]){ @autoreleasepool { return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class])); }}

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Called in the main entry point to create the application object, delegate and set up the event

cycle

UIApplicationDelegate

UIApplicationDelegate – protocol declares methods that are implemented by the delegate of the singleton UIApplication object.

AppDelegate – implements the application delegate to expose the control over the UIApplication

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UIApplication: States Application states:

Not Running – the app is not launched

Inactive – the app is running in the foreground but is currently not receiving events

Active – the app is running in the foreground but is receiving events

Background – the app is running in the background and executing code

Suspended – the app is in the background but is not executing code

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UIApplication: States (2)

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UIApplication – Launch Cycle

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UIViewController States

Overview and usage

Overview: UIViewController

UIViewController: Provides the fundamental view-

management model

Coordinates its efforts with model objects and other controller objects communication

Responsible for a single view

States preservation and restoration

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UIViewController – API (1)

Managing the View view – the root view of the

controller’s view hierarchy

viewDidLoad – it is called after the view controller has loaded its view hierarchy into memory

Handling Memory Warning didReceiveMemoryWarning

Sent to the view controller when the app receives a memory warning

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UIViewController – API (2)

Responding to View Events viewWillAppear

Notifies that its view to be added to a view hierarchy

viewDidAppear Notifies that that its view is added to

a view hierarchy

viewWillDisappear Notifies that its view is about to be

removed from a view hierarchy12

UIViewController – API (3)

viewDidDisappear Notifies that its view is about to be

removed from a view hierarchy

viewWillLayoutSubviews Called to notify the view controller

that its view is about to layout its subviews

viewDidLayoutSubviews Called to notify the view controller

that its view has just laid out its subviews 13

UIViewController - Lifecycle

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Questions?

iOS Application Lifecycle